The present invention relates generally to devices and methods for analyzing biological fluids. In particular, it relates to the design and use of improved centrifugal rotors having siphons which allow delivery of a precise volume of liquid to a chamber in the rotor.
Biological tests of blood plasma and other biological fluids frequently require that fluids be quickly divided into predetermined volumes for analysis in a variety of optical tests or assays. It is also frequently desirable to separate potentially interfering cellular components of the material from the other fluid prior to testing. Such measurement and separation steps have previously been typically performed by centrifugation to separate, for instance, blood plasma from the cellular components, followed by manual or automated pipetting of predetermined volumes of the blood plasma into separate test wells. Such procedures are labor intensive and time-consuming. As a result, various automated systems and methods have been proposed for providing multiple aliquots of plasma suitable for testing in a more efficient manner.
A major advance in the analysis of biological fluids has been the use of centrifugal rotors. These rotors are designed to measure volumes of a biological fluid, such as blood, remove cellular components, and mix the fluid with an appropriate diluent for analysis, for example by optical testing. Typically, the rotors provide a plurality of discrete volumes of sample in separate cuvettes in which the sample is optically analyzed.
To ensure accurate and consistent results, such rotors require the delivery of precisely measured volumes of liquid to various chambers in the rotor. This must often be accomplished in circumstances in which the rotor quickly accelerates and decelerates or is otherwise perturbed during operation. This perturbation can often lead to delivery of inaccurately measured volumes. The present invention addresses these and other needs.